The present invention relates to a system and method for packet-based communicating in a wireless telecommunications network, and particularly to switching packet signals within a cellular telecommunications network between a radio base station and a corresponding mobile switching center.
Wireless communication is one of the fastest growing and most demanding telecommunication applications. Cellular communications systems presently serve millions of cellular subscribers. A conventional cellular telecommunications network employs a circuit-switched architecture in which voice and data pass through physical switching devices in being routed between communicating devices. A conventional cellular telecommunications system, such as a Global System for Mobile Communication (GSM), may typically include a plurality of mobile switching centers (MSCs) which control the switching functions of the system. A plurality of radio base stations (RBSs) provide the radio interface to mobile stations in the network. Base station controllers (BSCs) provide control functions and physical links between the RBSs and the corresponding MSC.
In providing telecommunications services within a cellular telecommunication network, voice traffic is communicated between a mobile station and a destination terminal via the RBS, BSC and MSC serving the mobile station. If the destination terminal is another mobile station in the network, the voice traffic must also be sent to the other mobile station via the MSC, BSC and RBS corresponding thereto. As can be seen, a number of network devices are utilized in order to communicate with a mobile station using a circuit-switched architecture.
Packet-based communication technologies are becoming more prominent in communicating voice and other media. In part due to a move towards packet-based communication and to address increased traffic levels within physical switches in mobile telecommunication networks, there is a need to divert the handling and/or payload of voice traffic conventionally handled by the MSC.
The present invention overcomes the shortcomings in prior systems and thereby satisfies a significant need for a system and method for more effectively transporting packet-based media within a cellular telecommunications network.
According to a preferred embodiment of the present invention, there is provided a mobile telecommunications system including components which are commonly found in a conventional cellular network, including at least one mobile switching center (MSC) which performs conventional circuit switching functions for the system, a plurality of radio base stations (RBSs) which handle the radio interface to one or more mobile stations by allocating resources between the MSC and the mobile stations, and one or more base station controllers (BSCs) which provide the control functions and physical links between the MSC and each RBS served thereby.
According to the present invention, the mobile telecommunications network provides for the communication of packet-switched signals. Specifically, each RBS includes a device for converting voice signals received from a mobile station into packets and transports the packet signals to the intended destination. The RBS receives necessary identification information for the destination device, such as an address value and/or port number therefor. In addition, the RBS converts packet signals intended for the mobile station to signals suitable for subsequent transport thereto. By directing packet signals based upon voice signals from the mobile station to the appropriate destination as specified by the MSC and directing received packet signals to the mobile station, each RBS acts as a logical switch controlled by the MSC.
A method of communicating information, such as voice information, within the mobile telecommunications network includes performing a series of operations at system startup to initiate and/or establish communication between an RBS and the BSC and MSC associated therewith. A call setup routine is subsequently performed between the RBS and corresponding BSC and MSC upon initiation of a telephone call. The call setup routine includes the RBS communicating to the MSC (via the BSC) the mobile station port at the RBS over which a mobile station will communicate and the media port over which packet-based signals will be communicated with another terminal, and the MSC communicating to the RBS the remote media port associated with the other terminal with which communication will occur. Thereafter, the MSC is capable of controlling or otherwise maintaining the connection between the media port and mobile station port of the RBS and the communication of packet-based signals with the other terminal over the media port of the RBS.
Following the call set-up routine, voice signals are sent from the mobile station to the RBS, which receives the voice signals at the mobile station port and converts the signals into voice packet signals. The RBS then transports the packet signals to the other terminal over the media port. Voice packet signals transmitted by the other terminal and received by the RBS at the media port are converted into voice signals and transported to the mobile station over the mobile station port.
The present invention may also be directed to effectively communicating packet signals with a mobile station that is moving between different RBS devices during a handoff operation. If the moving mobile station leaves the cell served by a first RBS and enters a cell served by another RBS, communication occurs between the MSC and the two RBSs, resulting in the MSC maintaining the media port at the first RBS for communicating with the other terminal and establishing a relay connection between the first RBS and the second RBS presently serving the mobile station. In addition, the MSC controls the connection within the second RBS between the media port and the mobile station port associated with the mobile station. In this way, the first RBS is maintained as an xe2x80x9canchor RBSxe2x80x9d wherein packet information originating from the mobile station is transmitted from the second RBS to the first RBS over the relay connection and then to the other terminal, and packet information originating from the other terminal is transmitted to the first RBS and is then transmitted over the relay connection to the second RBS whereupon it is sent to the mobile station over the mobile station port of the second RBS.